Roman Longoria The goal of this book is to provide a useful and timely guide to the practitioner who designs or develops mobile applications. The contributors to this book are leaders in the user interface (UI) community actively working in mobile platform technol­ ogy and mobile application design. Thus, this book offers the reader unique insight into the latest technologies, market trends, design ideas, and usability data. We provide the reader with the latest information that will have direct and immediate impact on a broad scope of product design decisions, including those for voice, phone, and personal digital assistant (PDA) applications. In other words, this book is written by practitioners, for practitioners. When I approached my coauthors about writing a chapter, I had only a few criteria. First, each author should have unique experience and expertise about a certain aspect of mobile applications. Second, that the authors be able to provide an introduction to the technologies with which they work. Third, that each chapter include case studies and lessons learned from empirical usability evaluations. And fourth, that each author include in the chapter some fundamental knowledge that they wish they had known when they got started designing for the mobile context.